Radiographic apparatus

ABSTRACT

This invention relates to a radiographic apparatus which comprises a radiographic image photographing unit for photographing a radiographic image of an object irradiated with radiation by a radiation generating device, a distance measuring system for measuring the distances or distance from the radiation generating device to the radiographic image photographing unit and/or the object, and distance information indicating means for indicating distance information obtained by the distance measuring system.

This is a divisional application of application Ser. No. 09/008,510,filed Jan. 16, 1998 is now U.S. Pat. No. 6,502,984.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a radiographic apparatus forphotographing a radiographic image of an object in the medical field ornondestructive inspection field.

2. Related Background Art

(1) FIG. 1 is a diagram of a conventional radiographic apparatus. Aradiographic image photographing means 302 for photographing atransmitted radiographic image of an object S is disposed in front of aradiation generating means 301 as a radiation source for generatingradiation. The radiation generating means 301 and radiographic imagephotographing apparatus 302 irradiate radiation and photograph an imageof the object S on the basis of the photographing conditions, e.g., thetube voltage or tube current for an X-ray tube as the radiation source,irradiation time, and the like, set by the operator using aphotographing condition setting means 303.

(2) In X-ray radiography, X-rays that have scattered inside an objectlargely influence the image. In order to efficiently remove scatteredX-rays, a scattered X-ray removing grid (to be simply referred to as agrid hereinafter) is used to help improve the contrast and sharpness ofan X-ray image. The grid used can be classified into a parallel grid andconvergence grid depending on their structures. FIG. 2 is a sectionalview of the parallel grid, in which copper foils 391 and intermediatesubstances 390 are disposed to be parallel to each other and in adirection perpendicular to incoming X-rays. FIG. 3 is a sectional viewof the convergence grid, in which copper foils 391 and intermediatesubstances 390 are disposed to converge at a single point (in this case,a convergence point 401). The intermediate substance consists ofaluminum, wood, or the like.

(3) Conventional radiography uses a system as a combination of a filmand intensifying paper. In recent years, along with the development ofcomputers, various types of digital image photographing apparatuses havebeen developed and are used in clinical applications. A photographingapparatus using a photostimulable phosphor sheet as one of suchapparatuses temporarily records a radiographic image of an object S on aphotostimulable phosphor sheet, and then irradiates excitation lightsuch as a laser beam onto that photostimulable phosphor sheet to causestimulated emission. Based on an image signal obtained byphotoelectrically reading the emitted light, a radiographic image of theobject S is printed on a silver halide film or is displayed on a CRTdisplay.

On the other hand, a photographing apparatus using a photodetectionarray converts a radiographic image of the object S into a visible imagevia a scintillator or image intensifier, converts that visible imageinto an image signal via the photodetection array, and prints ordisplays the radiographic image of the object on a silver halide film orCRT display.

(4) Furthermore, in radiography in the medical field, in order to obtaina high-quality image without re-photographing, the radiographicconditions must be set to match the state and characteristics of theobject S. That is, the field of irradiation, quality, and exposure doseof radiation must be optimized, and appropriate image processes arerequired for a digital radiographic image to make it easier to see.

FIG. 4 shows the arrangement of a radiographic apparatus according tothe third conventional art. When a radiation generating means 301irradiates radiation onto an object S, the radiation isintensity-modulated and scattered in accordance with the internalstructure of the object S owing to interactions such as absorption,scattering, and the like of the object S with respect to the radiation,and then reaches a radiographic image photographing means 302 to obtaina radiographic image. Note that a grid 304 disposed in front of theradiographic image photographing means 302 removes scattered radiationto improve the contrast of the radiographic image.

In general, the radiographic image photographing means 302 comprises aphosphor CaWO₄ or the like that produces luminescence at an intensityproportional to the exposure dose, and a silver halide film, and theimage of the object S is recorded on the film as a latent image. Afterdevelopment, the recorded image is presented as a visible image thatgives a density proportional to the logarithm of the luminescenceamount, and is used in diagnosis, inspection, and the like.

Also, a computed radiography (CR) apparatus using an imaging plateapplied with a BaFBr:Eu phosphor and BaF:Eu phosphor which producephotostimulated luminescence is also used. The CR apparatus temporarilyrecords a radiographic image of the object S on the imaging plate, andthen irradiates excitation light such as a laser beam onto the imagingplate to cause stimulated emission. The apparatus prints or displays theradiographic image of the object S on a silver halide film or CRTdisplay on the basis of an image signal obtained by photoelectricallyreading the emitted light.

Furthermore, recently, a technique for reading a digital image using, asthe radiographic image photographing means 302, a photoelectricconversion device on which pixels each consisting of a very smallphotoelectric conversion element, switching element, and the like arearranged in a lattice pattern, has been developed.

(5) It is important in radiography to obtain a high-quality imagewithout re-photographing, and optimal radiographic conditions must beselected in correspondence with the state and characteristics of theobject S and those of the radiographic apparatus. That is, the field ofirradiation must be stopped down, and the dose and quality of radiationmust be optimized. Furthermore, when a radiographic image is to bedigitally processed, posture determination, edge extraction, and thelike of the object S are required.

In order to stop down the field of irradiation, a lead aperture stop isconventionally inserted immediately after the radiation generationdevice, and is manually moved. In order to confirm the divergence ofradiation, a visible light source is arranged at a position conjugatewith the radiation generating means 301, and the operator visuallychecks the degree of eclipse of the projected light by the aperturestop. In addition, in an X-ray radiography apparatus, the irradiationrange is confirmed in advance using a television monitor.

Upon setting the dose and quality of radiation, the photographer setsthem by determining proper conditions on the basis of the posture andphotographing portion of the object S, or inputs information associatedwith the posture and the photographing portion of the object S to theapparatus, which automatically sets proper conditions.

(a) However, in conventional art (1) above, since the operator must setoptimal photographing conditions to obtain a radiographic image which iseasy to observe, he or she must change the positional relationshipbetween the radiation generating means 301 and radiographic imagephotographing means 302 depending on the photographing method used, andmust measure the distance between them using a scale in every change.Furthermore, before the operator gains experience in using theapparatus, e.g., immediately after installation of the photographingapparatus, he or she must create an irradiation condition table or thelike and must photograph with reference to that table. Upon creating theirradiation condition table, the operator must make physical contactwith a patient as the object S to directly measure the breast thicknessusing a tool such as a breast meter or the like.

(b) When the grid described in conventional art (2) is used, grid cutoffoccurs. FIG. 5 shows the case wherein grid cutoff has occurred due tothe parallel grid, and illustrates an X-ray tube focal point F, andshadow images 414 a and 414 b on an image receiving surface 413 obtainedwhen X-rays are transmitted through lead foils 412 a and 412 b of a grid411. The lead foils 412 a is projected as a shadow image broader thanthat of the lead foil disposed in the direction of primary X-rays, whichdo not reach the image receiving surface accordingly. As a consequence,in an X-ray image, a portion where the broader shadow image is formedbecomes darker than a portion where it is not formed. The grid cutoffamount normally becomes larger as the grid ratio is higher and thedistance between the grid and X-ray tube focal point F is shorter.

Even when the convergence grid is used, if the positional relationshipbetween the X-ray tube focal point F and a convergence point 401 of thegrid is not proper, grid cutoff takes place. FIG. 6 shows an examplewherein the X-ray tube focal point F deviates horizontally from theconvergence point 401. In this case, since all the lead foils of thegrid cause equal grid cutoff of primary X-rays, an entirely and evenlydark X-ray image is obtained.

The grid is classified into a still grid and moving grid depending ontheir use methods. The still grid is used in the still state withrespect to an X-ray image receiving surface (to be simply referred to asan image receiving surface hereinafter), and the moving grid is builtand used in a device for moving the grid relative to the image receivingsurface to remove shadow images of the lead foils.

Even in a conventional apparatus using the moving grid, since the movingspeed of the grid is constant, the grid does not move at equal intervalsabout the center of the field of X-ray irradiation during the X-rayirradiation time, and the same result as that obtained by integratingthe horizontal deviation state within the irradiation time is obtained,i.e., a density pattern is formed in an X-ray image. On the other hand,when the photographing time is long and the grid must be reciprocallymoved, shadow images of the lead foils are often formed at the turningpoint positions.

(c) In conventional art (3) above, an apparatus which comprises imageprocess means for outputting an image with an optimal density andcontrast when overexposure or underexposure has occurred due tocondition setting errors upon photographing, or an apparatus whichcomprises determination means for determining the photographing posture,photographing portion, and field of irradiation of the object S tooptimally execute such image process is known. However, since theradiographic image of the object S is used in such determination, theimage size is as large as 1024×1024 samples and 12 bits required forquantization, thus requiring a long arithmetic time. Also, under theinfluences of scattered radiation, it is hard to accurately executepattern matching of the object S and recognition of the field ofirradiation.

(d) In conventional art (4) above, in order to stop down the field ofirradiation of radiation coming from the radiation generating means 301,a movable radiation aperture stop 305 inserted immediately before theradiation generating means 301 is manually adjusted. Furthermore, alight source 306 is arranged at a position conjugate with the radiationgenerating means 301, and the operator confirms the field of irradiationby visually observing the degree of eclipse of the projected light bythe movable radiation aperture stop 305. In this case, the operator muststand at the side of the radiation generating means 301, and must adjustthe width of the movable radiation aperture stop 305 every time theobject S changes, thus requiring very troublesome operations.Especially, in case of breast photographing, since front and side imagesof an identical object S must be alternately photographed, the operatormust adjust the width of the aperture stop in each photographing. Owingto such tedious operations, the operator may often photograph a sideimage with a small width without stopping down the movable radiationaperture stop 305.

However, when the side image of the object S is photographed withoutstopping down the movable radiation aperture stop 305, i.e., in thefull-open state, radiation also reaches an ineffective photographingregion, and so-called unintercepted radiation, which is not absorbed bythe human body, directly reaches a photo-timer light-receiving unit 307used for automatically controlling the dose. Hence, the uninterceptedradiation increases detection errors of the dose, and the dose cannot benormally detected.

Normally, the front and side images of the breast portion must bephotographed with different radiation qualities. However, at present,the operator must visually confirm the posture of the object and switchthe radiation tube voltage at the console of the radiation generationdevice to photograph the front and side images of the breast portion.

In the radiography apparatus combining a radiation image intensifier andtelevision camera, since radiographic observation is done on thetelevision monitor prior to film photographing, the radiation range canalso be visually confirmed. In this case, the operator need not stand atthe side of the radiation generating means, and can also adjust theaperture stop by remote control. However, when the object region is tobe extracted from the radiographic image of the object to automateaperture stop adjustment, the edges blur under the influences ofscattered radiation and the like, thus making region extractiondifficult. In addition, the object S is kept irradiated with radiationeven during radiographic observation.

On the other hand, in the CR apparatus using the imaging plate, thesignal level is detected by a coarse scan called a pre-scan using a veryweak laser beam, so as to extract the object region, thereby optimizingthe scan conditions for a main scan. However, since such processes aredone after photographing the object S, they are not helpful inoptimizing the photographing itself. Also, it is very hard to extractthe object region under the influences of scattered radiation and thelike as in the radiographic apparatus.

As described above, upon setting the photographing conditions and thelike for the radiographic apparatus, the operator visually observes theobject S, stops down the field of irradiation in correspondence with thesize of the object S, adjusts the radiation quality in accordance withfront and side shots, and manually switches the gain of a photo-timer.

However, since the radiographic apparatus depends on the operator toacquire information for recognizing the state and characteristics of theobject S, it is especially difficult for the apparatus to accuratelyrecognize the object region. The operator may often omit some settingoperations in units of objects S, e.g., operation for stopping down thefield of irradiation, to reduce his or her work loads. As a consequence,an image with inappropriate image quality may be obtained. For example,when radiation is irradiated even to an ineffective photographingregion, the photo-timer produces recognition errors under the influencesof unintercepted radiation, and a desired dose is not given. As aresult, an effective radiographic image cannot often be obtained. Sincethe amount of radiation that reaches the human body differs depending ona front image in which the object S becomes thin or a side image inwhich the object S becomes thick, an effective radiographic image cannotbe obtained unless the quality of radiation is switched, resulting inunnecessary radiation.

(e) In conventional art (5) above, in a photographing site with shorterphotographing cycles, e.g., in group diagnosis, it is cumbersome toadjust the position of a lead aperture stop every time the object Schanges. Especially, in breast photographing, the front and side imagesof one object S must often be alternately photographed, and adjustmentmust be done in each photographing. For this reason, photographing isoften done with the aperture stop fully open. When a side image with asmall width of the object S is photographed in such state, detectionerrors of the photo-timer of an automatic exposure means forautomatically controlling the radiation dose increase under theinfluence of unintercepted radiation that is not absorbed by the humanbody, and an appropriate radiation dose often cannot be obtained. As aresult, since sufficient object information cannot be obtained from theacquired image, photographing must be re-done.

Furthermore, although the radiation quality to be manually set must beoptimized to improve image quality, since the optimal conditions varydepending on different portions, postures, and the like of the object,it is very cumbersome to set the quality in units of objects as in thelead aperture stop. For this reason, all objects are often photographedunder identical conditions. Also, since the amount of scattered raysthat reach the human body differs depending on the object postures infront and side shots, the gain of the photo-timer must be switched toobtain an effective radiographic image. In either case, improperphotographing may result.

(f) In these conventional arts, it is consequently difficult toaccurately photograph in correspondence with the object.

SUMMARY OF THE INVENTION

It is the first object of the present invention to provide aradiographic apparatus which can solve the problems in conventional art(a) above, and can shorten the operation time by simplifying cumbersomeoperations that must be done by the operator.

It is the second object of the present-invention to provide an X-rayphotographing apparatus which determines the X-ray irradiation time bymeasuring the body thickness of an object before X-ray irradiation, andcontrols the moving grid on the basis of the determined X-rayirradiation time information to remove the influences of shadow imagesof lead foils formed in an X-ray image.

It is the third object of the present invention to provide aradiographic apparatus which can solve problems (c) in theabove-mentioned conventional art, and can output an optimal image athigh speed by performing image processes of a radiographic image.

It is the fourth object of the present invention to provide aradiographic apparatus which can solve problems (d) in theabove-mentioned conventional art, and determines optimal photographingconditions by easily acquiring two-dimensional information of the objectrequired for setting parameters for image processes of a radiographicimage.

It is the fifth object of the present invention to provide aradiographic apparatus which can solve problems (e) in theabove-mentioned conventional art, and can execute optimal radiography byacquiring object information immediately before photographing andreflecting it in setting of the photographing conditions.

It is the sixth object of the present invention to provide aradiographic apparatus which can execute appropriate radiographyaccurately corresponding to the situation of each object.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the arrangement of the first conventionalart;

FIG. 2 is an explanatory view of a parallel grid;

FIG. 3 is an explanatory view of a convergence grid;

FIG. 4 is a view showing the arrangement of the third conventional art;

FIG. 5 is an explanatory view of cutoff of the parallel grid;

FIG. 6 is an explanatory view of horizontal deviation of the convergencegrid;

FIG. 7 is a diagram showing the arrangement according to the firstembodiment of the present invention;

FIG. 8 is an explanatory view of automatic distance measurement;

FIG. 9 is a sectional view of a radiographic image photographing meansusing a silver halide film;

FIG. 10 is a sectional view of a radiographic image photographing meansusing a photostimulable phosphor;

FIG. 11 is a sectional view of a radiographic image photographing meansusing a photodetection array;

FIG. 12 is a diagram showing an electric circuit of a photodetectionunit;

FIG. 13 is a diagram showing the arrangement according to the secondembodiment of the present invention;

FIG. 14 is an explanatory view of body thickness measurement by means ofa rotary mirror;

FIG. 15 is an explanatory view of body thickness measurement by means ofa cylindrical lens;

FIG. 16 is an explanatory view of body thickness measurement by means ofa cylindrical mirror;

FIG. 17 is a diagram showing the arrangement according to the thirdembodiment of the present invention;

FIG. 18 is a graph showing the relationship between the breast thicknessand mAs value;

FIG. 19 is a diagram showing the arrangement according to the fourthembodiment of the present invention;

FIG. 20 is a diagram of an X-ray photographing apparatus according tothe fifth embodiment of the present invention;

FIG. 21 is an explanatory view of the principle of body thicknessmeasurement;

FIG. 22 is an explanatory view of an example using a rotary mirror;

FIG. 23 is an explanatory view of an example using a cylindrical lens;

FIG. 24 is an explanatory view of an example using a cylindrical mirror;

FIG. 25 is a diagram showing the arrangement of an X-ray irradiationtime determining means;

FIG. 26 is a graph showing the irradiation coefficient as a function ofobject thickness;

FIG. 27 is an explanatory view of a moving grid and its control means;

FIG. 28 is a view for explaining operation of the moving grid controlmeans;

FIG. 29 is a diagram showing the arrangement according to the sixthembodiment of the present invention;

FIG. 30 is a view showing the arrangement of a visible imagephotographing means;

FIG. 31 is an explanatory view of a radiographic sensing region;

FIG. 32 is an explanatory view of a CCD camera sensing region;

FIG. 33 is an explanatory view of a radiographic sensing region;

FIG. 34 is an explanatory view of a CCD camera sensing region;

FIG. 35 is a front view of posture determination;

FIG. 36 is a side view of posture determination;

FIG. 37 is an explanatory view of portion determination;

FIG. 38 is a view showing the arrangement according to the seventhembodiment of the present invention;

FIG. 39 is a perspective view of a radiographic unit using a pluralityof photoelectric conversion elements;

FIG. 40 is a perspective view of a radiographic unit using aphotodetection array;

FIG. 41 is a perspective view of a radiographic unit using a line sensorand its drive means;

FIG. 42 is a perspective view of a radiographic unit using a lighttransmission means and line sensor;

FIG. 43 is a perspective view of the light transmission means;

FIG. 44 is a view showing the arrangement according to the eighthembodiment of the present invention;

FIG. 45 is a view showing the arrangement according to the ninthembodiment of the present invention;

FIG. 46 is an explanatory view of object position information; and

FIGS. 47A and 47B are explanatory views of an object region informationprocess method.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described in detail hereinafter by way ofits embodiments illustrated in FIGS. 7 to 47A and 47B.

FIG. 7 is a diagram of a radiographic apparatus according to the firstembodiment. A radiographic image photographing means 11 forphotographing a radiographic image of an object S via the object S isdisposed in front of a radiation generating means 10 as a radiationsource for generating radiation, and an automatic distance measuringmeans 12 for measuring the distances or distance from the radiationgenerating means 10 to the radiographic image photographing means 11and/or the object S in a non-contact manner is disposed in the vicinityof the radiation generating means 10.

The output from a photographic or photographing condition setting means13, at which the operator controls irradiation by setting thephotographing conditions such as a tube voltage, tube current,irradiation time, and the like of an X-ray tube as the radiation source,is connected to the radiation generating means 10, and the output fromthe radiographic image photographing means 11 is connected to thephotographing condition setting means 13. The output from the automaticdistance measuring means 12 is connected to a distance informationindicating means 14 that indicates distance information.

The object S as a patient is located in front of the radiographic imagephotographing means 11, and the operator sets various photographingconditions at the photographing condition setting means 13. Radiationcoming from the radiation generating means 10 is transmitted through theobject S and reaches the radiographic image photographing means 11, thusphotographing a radiographic image of the object S. At this time, theautomatic distance measuring means 12 measures the distances or distancefrom the radiation generating means 10 to the radiographic imagephotographing means 11 and/or the object S in a non-contact manner, andpresents the distance information to the distance information indicatingmeans 14.

FIG. 8 is an explanatory view of distance measurement by the automaticdistance measuring means 12. The automatic distance measuring means 12comprises a light source 15 such as an LED, LD, or the like, aprojection optical system 16 for focusing a light beam coming from thelight source 15 to form a beam spot P on the observation surface, aposition detection element 17 such as a CCD, PSD, or the like, and animaging optical system 18 for imaging a beam spot image P′ on theposition detection element 17.

A light beam emitted by the light source 15 is focused by the projectionoptical system 16, and forms a small beam spot P on the observationsurface. The beam spot P is imaged on the position detection element 17by the imaging optical system 18 to form a beam spot image P′. Arelative distance Z from the beam spot image P on the observationsurface to the automatic distance measuring means 12 can be calculatedfrom the coordinate position of the beam spot image P′ on the positiondetection element 17.

In FIG. 8, assume that the principal point of the imaging optical system18 defines an origin O, the imaging plane of the position detectionelement 17 is set at a position of Z=−d, and the principal point of theprojection optical system 16 is set at a position of X=L. When a beamspot image P formed on the observation surface by a light beamirradiated in a φ direction with respect to the origin O is observedfrom the origin O in a θ direction, a relative distance D to the beamspot image P is given by:

D=(L×tan θ×tan φ)/(tan θ+tan φ)

If x represents the coordinate position of the beam spot image P′ on theposition detection element 17, then the angle θ is given by:

θ=tan⁻¹(x/d)

The distance from the radiation generating means 10 to the radiographicimage photographing means 11 is calculated from the above equation asthe relative distance D by projecting the beam spot P onto the frontsurface of the radiographic image photographing means 11, e.g., a breastcontact surface, and the distance from the radiation generating means 10to the object S is calculated by the above equation as the relativedistance D by projecting the beam spot P onto the surface of the objectS.

FIG. 9 is a sectional view when an X-ray photographing film changer 20is used as the radiographic image photographing means 11. Two filmpressure plates 22 a and 22 b on the inner surfaces of whichintensifying paper sheets 21 a and 21 b are adhered are disposed on theincoming side of radiation X. Upon photographing, a film F is sandwichedbetween the front and rear intensifying paper sheets 21 a and 21 b, andis tightly held by the front and rear film pressure plates 22 a and 22b.

A radiation intensity detection means 23 for detecting the intensity ofthe radiation X transmitted through the film F, and a vacuum pump 24 aredisposed behind these pressure plates, and a supply magazine 25 a forstoring unphotographed films F and a receive magazine 25 b for storingphotographed films F′ are disposed behind the pump 24. Above thesemembers, roller pairs 26 a, 26 b, and 26 c for conveying anunphotographed film F from the supply magazine 25 a to the photographingposition and conveying a photographed film F′ to the receive magazine 25b, and a motor 27 for driving these roller pairs 26 a, 26 b, and 26 care disposed.

Upon photographing using the film changer 20 with the above arrangement,the roller pairs 26 a and 26 b are driven by the motor 27 to pick up onefilm F from the unphotographed film storage supply magazine 25 a, andfeed it onto the front surface of the rear film pressure plate 22 badhered with the rear intensifying paper sheet 21 b. The rear filmpressure plate 22 b is driven in the direction of an arrow A by a rearfilm pressure plate drive mechanism (not shown), and the film F ispressed against the front intensifying paper sheet 21 a adhered on thefront film pressure plate 22 a. Furthermore, the film F is tightly heldby vacuum between the front and rear intensifying paper sheets 21 a and21 b upon operation of the vacuum pump 24. After the film F iscompletely tightly held between front and rear intensifying paper sheets21 a and 21 b and is ready to be photographed, radiation is irradiatedfrom the radiation generating means 10 upon operation of the operator,and a radiographic image of the radiation transmitted through the objectS is photographed.

Furthermore, in the radiographic image photographing means 11, theradiation transmitted through the object S enters the radiationintensity detection means 23 which detects its intensity. The radiationintensity information is set in a look-up table making means (to bedescribed later) and is used for making a look-up table.

FIG. 10 is a sectional view of the radiographic image photographingmeans 11 using a photostimulable phosphor sheet. This radiographic imagephotographing means uses a radiographic image informationrecording/reading device 30, which accumulates and records radiographicimage information on a photostimulable phosphor sheet P, irradiatesexcitation light onto the sheet to read image information by detectingstimulated emission in accordance with the accumulated and recordedimage information, and converts the image information into an electricalsignal to reproduce an image.

In this radiographic image information recording/reading device 30,endless belts 31 a, 31 b, 31 c, and 31 d for conveying a photostimulablephosphor sheet P are disposed along the four sides of a rectangle, andare connected to a transmission mechanism including, e.g., chains,gears, and the like (not shown), and a motor 32 serving as a drivesource. A reading means 35 is disposed in the vicinity of the endlessbelt 31 b. The reading means 35 comprises a laser light source 33 andphotomultiplier 34, and reads radiation information accumulated andrecorded on the photostimulable phosphor sheet P. A quenching means 37is disposed in the vicinity of the endless belt 31 d. The quenchingmeans 37 comprises a quenching light source 36 such as a fluorescentlamp, and the like, and makes the photostimulable phosphor sheet P emitresidual energy.

The residual energy on the photostimulable phosphor sheet P is emittedby quenching light coming from the quenching light source 36 in thequenching means 37. After that, the motor 32 is driven by a controlmeans (not shown) to drive the endless belts 31 a to 31 d via thetransmission mechanism, thereby conveying the photostimulable phosphorsheet P to the radiation incident position. The photostimulable phosphorsheet P irradiated with radiation X at the endless belt 31 a moves tothe endless belt 31 b where the reading means 35 is disposed. The laserlight source 33 irradiates a laser beam onto the photostimulablephosphor sheet P, and stimulated emission having an intensitycorresponding to the radiographic image information on thephotostimulable phosphor sheet P is received by the photomultiplier 34.In this manner, the radiographic image information accumulated andrecorded on the photostimulable phosphor sheet P is photoelectricallyread. The radiographic image information is transferred to a look-uptable making means (to be described later), and is used in making alook-up table. Also, the information is transferred to an image processmeans (not shown).

FIG. 11 is a sectional view of the radiographic image photographingmeans 11 using a photodetector array. A scintillator 60 is disposed atthe side of incoming radiation X, and a photodetector array 41 isdisposed in the neighborhood of the scintillator 60. The output from adrive circuit 42 is connected to the photodetector array 41.

Upon incidence of radiation X, the scintillator 60 obtains luminescencein the visible range based on binding energy obtained when the hostlattice of a phosphor is excited by high-energy X-rays and recombines.Note that this luminescence is produced by the lattice itself such asCaWO₄, CdWO₄, or the like, or by a luminescence center substance such asCsI:Tl, ZnS:Ag, or the like activated in the lattice. The drive circuit42 drives the photodetector array 41 to convert photons into electricalsignals to read out electrical signals from the individual pixels. Theradiographic image information obtained by the drive circuit 42 istransferred to a look-up table making means (to be described later) andis used in making a look-up table. Also, the radiographic imageinformation is transferred to an image process means (not shown).

FIG. 12 shows the arrangement of the equivalent circuit of thephotodetector array 41. In this circuit, a two-dimensional amorphoussilicon sensor is used as a detection element. However, when otherelements such as a solid-state imaging element such as a charge-coupleddevice, a photoelectric intensifier, and the like are used, the functionand arrangement of the A/D converter remain the same.

One element in the photodetector array 41 is made up of a photodetectionunit 50 and a switching TFT 51 for controlling accumulation and readingof a charge, and normally consists of amorphous silicon (αSi) formed ona glass substrate. A capacitor 52 in the photodetection unit 50 maysimply comprise a photodiode having a parasitic capacitance, or maycomprise a parallel circuit of a photodiode 53 and an additionalcapacitor 52 for improving the dynamic range of the detector.

The anode A of the photodiode 53 is connected to a bias wiring line Lbas a common electrode, and its cathode K is connected to thecontrollable switching TFT 51 used for reading out a charge accumulatedon the capacitor 52. The switching TFT 51 is a thin film transistorconnected between the cathode K of the photodiode 53 and a chargereading amplifier 54. A parallel circuit of a capacitive element 55 anda reset switching element 56 is connected between the switching TFT 51and the amplifier 54.

The reset switching element 56 is enabled by the switching TFT 51 andthe signal charge to reset the capacitor 52. After that a chargecorresponding to the radiation dose is produced in the photodiode 53upon receiving radiation, and is accumulated on the capacitor 52. Thereset switching element 56 is enabled again by the switching TFT 51 andthe signal charge to transfer the charge to the capacitive element 55,and the charge amount accumulated by the photodiode 53 is read out bythe amplifier 54 as a potential signal. The potential signal isA/D-converted to detect the incoming radiation dose.

FIG. 13 is a diagram showing the arrangement of a radiographic apparatusaccording to the second embodiment of the present invention. An objectthickness arithmetic means 60 is connected between the automaticdistance measuring means 12 and distance information indicating means 14shown in FIG. 7, and calculates the body thickness of the object S onthe basis of the distances or distance from the radiation generatingmeans 10 to the radiographic image photographing means 11 and/or objectS. Other arrangements are the same as those in the first embodiment.

The body thickness of the object S is calculated from the differencebetween the relative distance between the radiographic imagephotographing means 11 and automatic distance measuring means 12, thatis obtained by projecting a beam spot onto the front surface, e.g., thebreast contact surface, of the radiographic image photographing means11, and the relative distance between the object S and automaticdistance measuring means 12, that is obtained by projecting a beam spotonto the object S. The distance information indicating means 14indicates the distance information obtained by the automatic distancemeasuring means 12 and/or the object thickness information obtained bythe object thickness arithmetic means 60.

In the above-mentioned embodiment, a beam spot is projected onto theobject S, and the distance to that point is calculated. Alternatively,as shown in FIG. 14, a laser beam emitted by a light source 61 may bescanned as a beam spot on the object S using a rotary mirror 62, so thatthe body thickness of a light sectional plane of the object S can bemeasured. Also, as shown in FIG. 15, a laser beam emitted by the lightsource 61 may be expanded to a single band using a cylindrical lens 63,and be projected onto the object S, so that the body thickness of thelight sectional plane of the object S can be measured. Similarly, asshown in FIG. 16, a laser beam emitted by the light source 61 may bereflected by a cylindrical mirror 64 to measure the body thickness ofthe light sectional plane of the object.

FIG. 17 is a diagram showing the arrangement of a radiographic apparatusaccording to the third embodiment. The radiographic image photographingmeans 11, the photographing condition setting means 13 represented by,e.g., a keyboard, and the automatic distance measuring means 12 areconnected to a look-up table making means 65, which makes a look-uptable using one or both data. In the following description, a detaileddescription of the same portions as those in the first and secondembodiments will be omitted.

FIG. 18 is a graph serving as a look-up table, which shows therelationship between the mAs value (tube current×irradiation time) andthe breast thickness of a patient as the object S. FIG. 18 plots the mAsvalue versus breast thickness for tube voltages of 100 and 120 kVp whenthe intensity information or radiographic image information of radiationtransmitted through patients respectively having breast thicknesses of17, 18, 19, 20, 21, 22, and 23 cm outputs a constant value, andapproximates the plotted values by an exponential function or quadraticfunction.

FIG. 18 exemplifies the relationship between the mAs value and breastthickness for seven patients with different breast thicknesses.Alternatively, when the relationship between the mAs value and breastthickness is obtained and averaged for a larger number of patients, alook-up table can be made more accurately. Also, the look-up table maybe made using a phantom consisting of a substance having a transmittanceequivalent to that of human body without using actual patient data.

The look-up table can also hold, as information, all or some of thefollowing photographing conditions such as the photographing distance,photographing portion, photographing posture, thickness of the object S,type of intensifying paper, type of film, type of scattered radiationremoval filter, type of additional filter, and the like, in addition tothe tube voltage, breast thickness, and mAs value. For example, anapproximation function formula representing the relationship between thebreast thickness and mAs value for each tube voltage, and all or some ofnumerical values obtained by such approximation function formula may beheld in a memory or a recording medium such as an HDD.

FIG. 19 is a diagram showing the arrangement of a radiographic apparatusaccording to the fourth embodiment. A photographing condition automaticdetermining means 66 is connected to the radiation means 10,radiographic image photographing means 11, photographing conditionsetting means 13, and object thickness arithmetic means 60. In thefollowing description, a detailed description of the same portions asthose in the first to third embodiments will be omitted.

When the photographing condition automatic determining means 66determines the photographing conditions using the look-up table shownin, e.g., FIG. 18, in an irradiation time determining mode in which theoperator sets the tube voltage and tube current using the photographingcondition setting means 13, and the photographing condition automaticdetermining means 66 determines the irradiation time, if, for example,the tube current and tube voltage are respectively set at A (mA) and 100(kVp) by the photographing condition setting means 13, and the objectthickness arithmetic means 60 measures 21.5 (cm) as the breast thicknessof a patient, the mAs value need only be set at 2.9 with reference tothe look-up table, and an irradiation time T (sec) can be determined by2.9/T.

On the other hand, in a tube current determining mode in which theoperator sets the tube voltage and irradiation time at the photographingcondition setting means 13 and the photographing condition automaticdetermining means 66 determines the tube current, if, for example, theirradiation time and tube voltage are respectively set at T (sec) and100 (kVp) by the photographing condition setting means 13, and theobject thickness arithmetic means 60 measures 21.5 (cm) as the breastthickness of a patient, the tube current (mA) can be determined by2.9/T.

Furthermore, in a tube voltage determining mode in which the operatorsets the tube current and irradiation time at the photographingcondition setting means 13 and the photographing condition automaticdetermining means 66 determines the tube voltage, if, for example, thetube current and irradiation time are respectively set at 40 (mA) and0.05 (sec) by the photographing condition setting means 13, i.e., themAs value is 2, and the object thickness arithmetic means 60 measures21.5 (cm) as the breast thickness of a patient, the tube voltage can bedetermined to be 100+{α/(α+β)}×(120−100) (kVp) from the ratio α:β atintersections c of 2 mAs and the breast thickness of 21.5 (cm) for 100(kVp) and 120 (kvP), with reference to the look-up table. When a look-uptable holds information for more tube voltages, e.g., those in 5 (kVp)increments, the tube voltage can be determined more accurately.

FIG. 20 is a diagram showing an X-ray photographing apparatus accordingto the fifth embodiment of the present invention. As shown in FIG. 20,the apparatus comprises an X-ray irradiation means 111 for generatingX-rays, a grid 118 which is arranged in front of the irradiation means111 and removes scattered X-rays, a moving grid means 112 fortranslating the grid 118, and an X-ray photographing means 113 forphotographing an X-ray image transmitted through the grid 118. The X-rayphotographing means 113 is a device using, e.g., a screen film,photostimulable phosphor, solid-state imaging element, or the like as anX-ray image receiving surface.

An object thickness measuring means 114 for measuring the body thicknessof the object S, and an X-ray radiation or irradiation time determiningmeans 115 for determining the X-ray irradiation time on the basis of theobject thickness information obtained by the object thickness measuringmeans 114 are connected to an X-ray radiation or irradiation controlmeans 116 and a moving grid control means 117. The X-ray irradiationcontrol means 116 controls the X-ray irradiation means 111 on the basisof the X-ray irradiation time. Also, the moving grid control means 117controls the moving grid means 112 on the basis of the determined X-rayirradiation time.

FIG. 21 shows the principle of thickness measurement by the objectthickness measuring means 114. A light beam emitted by a light source121, e.g., a laser diode is focused by a projection optical system 122,and forms a small beam spot P on the observation surface. This beam spotP is imaged on a position detection element 124, e.g., a CCD sensor, byan imaging optical system 123, and forms a beam spot image p. A relativedistance Z between the beam spot P on the observation surface and theobject thickness measuring means 114 can be calculated from thecoordinate position of the beam spot image p on the position detectionelement 124.

Assume that the principal point of the imaging optical system 123defines an origin O, the imaging plane of the position detection element124 is set at a position of Z=−d, and the principal point of theprojection optical system 122 is set at a position of X=L. When the beamspot P formed on the observation surface by a light beam irradiated in aφ direction with respect to the origin O is observed from the origin Oin a θ direction, a relative distance D to the beam spot P is given by:

D=L/(tan θ+tan φ)

The angle θ is given by:

θ=tan⁻¹(x/d)

where x is the x-coordinate of the beam spot image p on the positiondetection element 124.

The body thickness of the object can be calculated from the differencebetween the relative distance between the X-ray photographing means 113and object thickness measuring means 114, that is obtained by projectinga beam spot onto, e.g., the X-ray photographing means 113, and therelative distance between the object S and object thickness measuringmeans 114, that is obtained by projecting a beam spot onto the object S.

In the above-mentioned method, a beam spot is projected onto the object,and the distance to that point is calculated. Alternatively, as shown inFIG. 22, a laser beam emitted by a light source 131 may be scanned as abeam spot on the object using a rotary mirror 132, so that the bodythickness of a light sectional plane of the object can be measured.

Also, as shown in FIG. 23, a laser beam emitted by a light source 141may be expanded to a single band using a cylindrical lens 142, and beprojected onto the object, so that the body thickness of the lightsectional plane of the object can be measured.

Furthermore, as shown in FIG. 24, a laser beam emitted by a light source151 may be reflected by a cylindrical mirror 152 to measure the bodythickness of the light sectional plane of the object.

FIG. 25 shows an example of the diagram of the X-ray irradiation timedetermining means. The body thickness information measured by the objectthickness measuring means 114, and photographing condition informationsuch as a photographing portion, tube voltage, tube current, and thelike, input at a photographing condition input means 161 such as acontrol panel, are input to the X-ray irradiation time determining means115. The X-ray irradiation time determining means 115 determines theX-ray irradiation time with reference to a look-up table 162 that holdsthe irradiation conditions with respect to the body thickness of theobject at each tube voltage, and outputs the X-ray irradiation timeinformation to the X-ray irradiation control means 116 and the movinggrid control means 117.

FIG. 26 is a graph showing an example of the look-up table 162 thatshows an irradiation coefficient K as a function of object thickness. Ifd₁ is the reference body thickness, I₁ the dose to be irradiated, d₂ thebody thickness of the object to be photographed, I₂ the dose to beirradiated onto the object to obtain an identical density, then theirradiation coefficient K is given by:

K=I ₂ /I ₁ =Ie ^(μd2) /Ie ^(μd1) =e ^(μ(d2−d1))

where I is the dose transmitted through the object, μ the attenuationfactor of the object, and e the base of the natural logarithm.

That is, in order to obtain a reference density in objects withdifferent body thicknesses d₂, a dose corresponding to a multiple of thefollowing value is required:

e^(μ(d2−d1))

In this manner, the X-ray irradiation time determining means 151 obtainsa value I₁×K with reference to the look-up table 162 on the basis of thetube current information A and tube voltage information input at thephotographing condition input means 161, and can determine the X-rayirradiation time T by:

T=I ₁ ×K/A

FIG. 27 shows an example of the arrangement of the grid 118, moving gridmeans 112, and moving grid control means 117. The moving grid means 112comprises, e.g., a rotary motor 181, and a plate cam 182 for convertingrotation of the rotary motor 181 into reciprocal motion. When aconvergence grid having a convergence distance of f cm and a grid ratior:1 is moved horizontally by b cm, the primary X-ray loss (%) is givenby:

L=r×b/f×100(%)

For example, when photographing is done using a grid having aconvergence distance of 180 cm and a grid ratio 12:1, if the primaryX-ray loss is to be reduced to 10% or less, the horizontal movement mustbe suppressed to 1.5 cm or less from the above equation.

The grid is moved by the same width on both sides of the center of thefield of irradiation of X-rays during X-ray irradiation so as toequalize cutoff on the X-ray image. The moving grid control means 117controls the rotary motor 181 to move the grid by predetermined widthson both sides of the center of the field of irradiation of X-rays duringX-ray irradiation.

When the rotary motor 181 satisfies a given condition, the X-rayirradiation control means 116 controls to irradiate X-rays for the X-rayirradiation time determined by the X-ray irradiation time determiningmeans 115. For example, as shown in FIG. 28, if the X-ray irradiationtime determining means 115 determines the X-ray irradiation time=T, 2 brepresents the moving distance of the grid, and R the radius of rotationof the rotary motor 181, then the angle 2θ of rotation of the rotarymotor 181 during the X-ray irradiation time T is:

2θ=sin⁻¹(b/R)×2

Hence, the moving grid control means 117 controls the rotary motor 181to rotate 2θ during the X-ray irradiation time T.

The X-ray irradiation control means 116 controls to irradiate X-rays ata position where the contact point between the grid and plate cam 182 isθ before the center of the field of irradiation of X-rays, or at aposition a delay time before θ in consideration of the system delay.

By minimizing the moving distance 2 b of the grid during the X-rayirradiation time, for example, to 1 cm or less, the influence of gridcutoff can be removed.

As described above, according to this embodiment, since the bodythickness of the object is measured before irradiation of radiation, theirradiation time is determined, and the moving grid is controlled on thebasis of the irradiation time information, thus removing the influencesof shadow images of lead foils formed in a radiographic image andproviding a radiographic image which is easy to observe.

FIG. 29 is a diagram showing a radiographic apparatus according to thesixth embodiment. A radiographic image photographing means 71 isdisposed in front of a radiation generating means 70 for generatingradiation. The radiographic image photographing means 71 uses aphotostimulable phosphor, photodetection array, or the like as an imagereceiving surface. A visible image photographing means 72 forphotographing a visible image of an object S is disposed in the vicinityof the radiation generating means 70.

The output from the radiographic image photographing means 71 isconnected to an image process means 73, which has image processfunctions of histogram analysis, gradation correction, frequencyemphasis, and the like of image information obtained by the radiographicimage photographing means 71. The output from the visible imagephotographing means 72 is connected to a position corresponding means74, which also receives the output from the radiographic imagephotographing means 71. Furthermore, the output from the visible imagephotographing means 72 is connected to an image process conditiondetermining means 75, the output of which is connected to the imageprocess means 73. With this arrangement, the image process conditiondetermining means 75 has a function of determining the image processconditions of the image process means 73 on the basis of visible imageinformation obtained by the visible image photographing means 72.

FIG. 30 shows the arrangement of the visible image photographing means72. The visible image photographing means 72 comprises a return mirror77 having high transmittance with respect to radiation, a CCD camera 78,and a movable aperture stop 79 for adjusting radiation to an arbitrarysize. The CCD camera 78 has, e.g., 512×512 pixels and requires 8 bitsfor quantization, and can obtain a visible image that can be processedby black-and-white and versatile image process devices. Note that inFIG. 30 the optical axis of radiation agrees with that of the visibleimage photographing means 72, but they need not agree with each other aslong as the positional relationship is appropriately calibrated.

With this arrangement, the radiation generating means 70 emits radiationtoward the object S, and the radiation transmitted through the object Sreaches the radiographic image photographing means 71, thusphotographing a radiographic image. The radiographic image is subjectedto image processes in the image process means 73 to obtain radiographicimage information of the object S having a sensing region B, as shown inFIG. 31. On the other hand, the CCD camera 78 of the visible imagephotographing means 72 photographs a visible image of a sensing regionC, as shown in FIG. 32.

For example, with reference to a mark M on the radiation incoming sideof the radiographic image sensing means 71, the sensing region B of theradiographic image photographing means 71 is made to correspond to thesensing region C of the CCD 78, and the coordinate positions of visibleimage information obtained by the visible image photographing means 71and image information obtained by the radiographic image photographingmeans 71 can be made to correspond to each other by the positioncorresponding means 74. Note that the visible information andradiographic information do not always have one-to-one correspondencetherebetween. For example, if the visible information consists of512×512 pixels, and radiographic information consists of 1024×1024pixels, one pixel in the visible information corresponds to four pixelsin the radiographic information. On the other hand, since the visibleimage information is imaged by a lens, the peripheral portion of theimage may often be distorted. In such case, the distortion is preferablycorrected before determining the correspondence with the radiographicinformation.

When the image process condition determining means 75 comprises anirradiation field determining means for determining the field ofirradiation, since the field of irradiation can be adjusted to anarbitrary size by the movable aperture stop 79 of the radiationgenerating means 70, the radiographic sensing region B is divided intoan irradiated region B1 and a non-irradiated region B2 masked by themovable aperture stop 79, as shown in FIG. 33. Furthermore, as shown inFIG. 34, the visible image information photographed by the visible imagephotographing means 72 is divided into an irradiation field region C1and a non-irradiation field region C2 by binarization, as shown in FIG.34. Since these regions C1 and C2 can be made to correspond to theregions B1 and B2 of the radiographic image information by the positioncorresponding means 74, the image process means 73 performs imageprocesses on the irradiation field region B1 of the radiographic imageinformation.

When the image process condition determining means 75 comprises aposture determining means for determining the postures of the object Sin front and side shots, front and side shot images D and E of visibleimage information obtained by the visible image photographing means 72are respectively divided into object regions D1 and E1, and non-objectregions D2 and E2 by binarization, as shown in FIGS. 35 and 36. Forexample, whether a front or side shot D or E is to be obtained isdetermined on the basis of the widths (the lengths of double-headedarrows in FIGS. 35 and 36) of the object regions D1 and E1 and/orsymmetry about the centers (one-dashed chain lines in FIGS. 35 and 36)of images and/or the presence/absence of the arms, and the like. Then,the determined posture information is supplied to the image processmeans 73, which executes image processes suitable for the object regionsD1 and E1.

Finally, when the image process condition determining means 75 comprisesa photographing portion determining means for determining thephotographing portion of the object S, a binary image F shown in FIG. 37is generated by visible image information obtained by the visible imagephotographing means 72 by binarization. The binary image F is comparedwith a head template G1, breast template G2, and hand template G3. Forexample, errors between the binary image F and the individual portiontemplates G1, G2, and G3 are calculated in units of pixels, and the sumtotals of errors are compared with a predetermined threshold value. Whenthe sum total is smaller than the threshold value, the correspondingportion is determined to be the photographing portion. The portioninformation is then supplied to the image process means 73, whichexecutes an image process suitable for the photographing portion in theobject region of radiographic image information. Note that the head,breast, and hand alone have been described, but the abdomen, leg, andthe like can be similarly determined.

FIG. 38 shows the arrangement of a radiographic apparatus according tothe seventh embodiment of the present invention. A return mirror 81,movable aperture stop 82, object S, and radiographic unit 83 aredisposed in turn in front of a radiation generating means 80, and alight source 84 is disposed in the incident direction of the returnmirror 81. The radiographic unit 83 comprises a grid 85, photo-timerlight-receiving unit 86, and radiographic image photographing means 87.The difference between this embodiment and the third embodiment shown inFIG. 4 is that an object information acquiring means 88 comprising avisible light sensor for obtaining two-dimensional information of theobject S is disposed in front of the radiographic image photographingmeans 87.

In this manner, since the object information acquiring means 88 isarranged, one-to-one correspondence with the radiographic imagephotographing means 87 can be obtained. Hence, the radiographic image ofthe object S and two-dimensional information can be easily made tocorrespond to each other, and such system is particularly effective fora portable radiographic unit 83. Note that the wavelength range of lightto be used in practice is not limited to visible light as long as it isnot harmful to the human body.

FIGS. 39 to 43 are perspective views of the object information acquiringmeans 88. FIG. 39 shows the object information acquiring means 88 madeup of a plurality of photoelectric conversion elements 89 assemiconductor elements of, e.g., CdTe or the like. An object receptioncover 90 which is transparent with respect to light is disposed in frontof the object information acquiring means 88 so as to prevent the objectS from directly touching the object information acquiring means 88. FIG.40 shows the object information acquiring means 88 made up of aphotodetection array 91 as a photoelectric conversion surface sensor of,e.g., amorphous silicon (αSi) or the like. FIG. 41 shows the objectinformation acquiring means 88 made up of a line sensor 92 as a linearphotoelectric conversion element and a drive means 93. By driving theline sensor 92 in a direction perpendicular to its scanning direction,two-dimensional information of the object S can be acquired. The drivemeans 93 in this case comprises guide drive screws and a drive motor,and the line sensor 92 is retracted outside the irradiation region ofradiation during irradiation.

Furthermore, FIG. 42 shows the object information acquiring means 88made up of a light transmission means 94, and a line sensor 95 as alinear photoelectric conversion element. In this case, the line sensor95 is attached to the end face of the light transmission means 94 toefficiently receive light coming from the light transmission means 94.The light transmission means 94 is constituted by stacking rods 96consisting of a material having uniform radiation absorbency such as anacrylic resin in correspondence with the number of pixels of the linesensor 95, and these stacked rods 96 have different light incidentpositions to obtain two-dimensional information of the object S inaccordance with the light incidence pattern.

FIG. 43 is a perspective view of the light transmission means 94. Eachrod 96 is divided into two pieces to intercept transmission of light,and has opening portions 97 that receive light. Line sensors 97 aslinear photoelectric conversion elements are attached to the two endfaces of the light transmission means 94, thus obtaining a doubleinformation amount.

Such object information acquiring means 88 can obtain two-dimensionalinformation of the object S on the basis of the silhouette image of theobject S or the presence/absence of incoming light when the light isintercepted by the object S. When the light source 84 that emits visiblelight or infrared light shown in FIG. 38 is turned on, two-dimensionalinformation of the object S can be obtained more clearly. On the otherhand, when a marginal light correction means for correcting theinfluences of marginal light and ambient light other than illuminationlight coming from the light source 84 is used, two-dimensionalinformation of the object S can be obtained further clearly bysubtracting the marginal light information obtained by the objectinformation acquiring means 88 when the light source 84 is OFF from theincoming light information obtained by the object information acquiringmeans 88 when the light source 84 is ON.

In this manner, since the object information acquiring means 88 usesvisible light or infrared light, it is not harmful to the human body.Also, when visible information acquired by the object informationacquiring means 88, e.g., the silhouette image, is displayed on atelevision monitor, remote control is also allowed.

FIG. 44 shows the arrangement of a radiographic apparatus according tothe eighth embodiment of the present invention. A photographingcondition determining means 99 for determining the photographingconditions on the basis of two-dimensional information of the object Sobtained by the object information acquiring means 88 is added to theradiographic apparatus of the seventh embodiment.

The photographing condition determining means 99 determines thephotographing conditions on the basis of the two-dimensional informationof the object S in the following order.

(1) The means 99 determines the posture, i.e., the front or side shot ofthe object S, and determines the quality of radiation, i.e., theradiation tube voltage.

(2) The means 99 determines the portion of the object S and determinesthe quality of radiation.

(3) The means 99 determines the irradiation range and determines theaperture range of the movable aperture stop 82.

(4) The means 99 determines the photographing range of the object S.

(5) The means 99 determines the effective region of the photo-timerlight-receiving unit 86.

(6) The means 99 determines the gain of a photo-timer.

(7) The means 99 determines the read range when radiographic imageinformation is read out from the radiographic image photographing means97.

(8) The means 99 determines the process parameters used when theradiographic image information read out from the radiographic imagephotographing means 97 is subjected to an image process.

(9) The means 99 determines the size of a film used for outputting theradiographic image information via a laser printer or the like.

In this manner, since the photographing condition determining means 99uses the two-dimensional information of the object S, the influences ofblurring caused by scattered radiation of the radiographic imageinformation can be removed, and processes such as edge extraction andthe like can be easily done. Hence, the photographing conditions can bedetermined appropriately.

In the seventh and eighth embodiments described above, thetwo-dimensional information of the object S required for setting thequality and dose of the radiation generating means 80, setting themovable aperture stop 82, and setting image process parameters of aradiographic image for edge extraction and the like of the object S canbe easily acquired, and the photographing conditions such as the qualityand dose of the radiation generating means 80, setup of the movableaperture stop 82, and the like can be accurately and easily determinedon the basis of the acquired two-dimensional information of the objectS.

FIG. 45 shows the arrangement according to the ninth embodiment of thepresent invention. A return mirror 101 having high transmittancecharacteristics with respect to X-rays, movable aperture stop 102,object S, and radiographic means 104 having a photo-timerlight-receiving unit 103 are disposed in turn in front of an X-ray tube100 for emitting X-rays, and an imaging lens 105 and CCD camera 106 aredisposed in the reflecting direction of the return mirror 101. When thisradiographic apparatus photographs an image of the breast portion of thehuman body as the object S, and acquires object information useful formedical purposes from the photographed image, optimal conditions of thefield of irradiation can be automatically set.

The X-ray tube 100 emits radiation toward the object S, and theradiographic means 104 obtains an image of the radiation intensitydistribution transmitted through the object S. The photo-timerlight-receiving unit 103 performs radiation input suitable for thephotographing apparatus sensitivity characteristics, and preventsabnormal breast exposure. That is, the unit 103 transmits an irradiationstop signal to a controller of the X-ray tube 100 upon detecting a doseoptimal for photographing. The movable aperture stop 102 interceptsirradiation onto an ineffective region in breast radiography, and avoidsoperation errors of the photo-timer light-receiving unit 103 andirradiation excessive for radiography. On the other hand, the CCD camera106 observes a visible object image via the imaging lens 105 and returnmirror 101 so as to obtain object position information without anyirradiation.

In order to determine the effective field of irradiation and toautomatically set optimal conditions of the actual field of irradiationin radiography, i.e., actual photographing, the CCD camera 106photographs an object image before the actual photographing, andacquires object position information based on an object image S′ shownin FIG. 46. An actual photographing image receiving region H2 obtainedwhen the movable aperture stop 102 is fully open is present inside aphotographing region H1 of the CCD camera 106, and a background image T′is present on the background of the object image S′. The backgroundimage T′ preferably has a color tone different from that of the objectimage S′ in correspondence with the light-receiving characteristics ofthe CCD camera 106 so that it can be easily distinguished from theobject image S′, and the object region can be accurately and easilyextracted. An object region extraction means which binarizes the objectimage S′ and background image T′ in the actual photographing imagereceiving region H2 from the object position information on the basis ofthe color tone or the like extracts an object region S1, as shown inFIG. 47A.

Subsequently, using an optimal photographing condition determiningmeans, a proper irradiation field determining means in a breast shot incase of this embodiment, a proper field L of irradiation in actualphotographing is determined. By accumulating the object region S1extracted from the front shot image in the vertical direction, ahistogram is generated, as shown in FIG. 47B, and arm regions withsmaller distributions in the vertical direction are determined toidentify the breast portion. However, in an object S with no armportions like in a side shot image, this procedure is omitted. Incorrespondence with the width of the remaining breast portion, anoptimal target field L of irradiation is determined as indicated bymovable aperture stop edges N1 and N2 in FIG. 47A.

Finally, the movable aperture stop 102 is automatically set to completepreparation for actual photographing. When the photographer does notwant to perform automatic setting, the optimal field L of irradiationmay be compared with the current irradiation state to determine thedegree of mismatch using a threshold value, and the determination resultmay be displayed as a warning message.

In this embodiment, the object position information acquiring means usesthe CCD camera 106 and imaging lens 105. In place of the CCD camera 106,a two-dimensional image sensing tube may be used. On the other hand, theoptical axis of radiation agrees with that of the object positioninformation acquiring means, but they need not agree with each other aslong as the actual photographing image receiving position isappropriately calibrated. Furthermore, the object position informationacquiring means may obtain the intensity distribution on a photographingsurface by means of laser scanning and a photosensor for receiving thereflected laser beam, or may receive the projected object distributionby means of existing illumination, and an optical fiber array andphotosensor arranged in front of the photographing surface. In thisembodiment, the movable aperture stop 102 is movable in only thehorizontal direction. However, in order to protect the head and abdomenportions, the movable aperture 102 may also be disposed in the verticaldirection.

As described above, in the ninth embodiment, the object region S1 can beeasily and accurately extracted immediately before actual photographing,and optimal photographing conditions in actual photographing areautomatically set and indicated, thus preventing actual photographingerrors under improper photographing conditions. The object region S1 canbe extracted immediately before actual photographing, and the field ofirradiation optimal to actual photographing can be automatically set andindicated to the photographer. Furthermore, the effective region of thephoto-timer light-receiving unit 103 can be determined based on theobject region S1. Also, the posture of the object S in front or sideshot is determined based on the object region S1, and the gain of thephoto-timer can be determined in correspondence with the determinedposture. Moreover, by comparing the object region S1 with a look-uptable prepared in advance, the photographing portion can be determined,and the tube voltage corresponding to the photographing portion can beautomatically set and indicated to the photographer. Hence, actualphotographing errors due to an insufficient exposure amount can beprevented.

In order to prevent operation errors under the influences ofunintercepted radiation, a radiographic apparatus which automaticallysets optimal conditions of the photo-timer light-receiving region may beused. In this case, the object position information acquiring means andobject region extraction means of the ninth embodiment are used toextract the edge of the breast portion of the object. Using an optimalcondition determining means which does not use any portion other thanthe object region within the light-receiving region of the photo-timerlight-receiving unit 103, weights the light-receiving region, or thelike, the effective region of the photo-timer in actual photographing isdetermined and is automatically set.

In order to correct the difference in scattered radiation in front andside shots, the photo-timer gain may be automatically switched. Theobject position information acquiring means and object region extractionmeans of the ninth embodiment are used to extract the edge of the breastportion of the object. By determining the width, symmetry, andpresence/absence of arm portions of the object S using a thresholdvalue, a front or side shot is determined, and the photo-timer gain isswitched to a prescribed value for the front or side shot. In order toprevent determination errors, the determination result may be merelyindicated to the photographer using a display means.

Furthermore, the quality of radiation that optimizes the object contrastin the radiographic image depending on the photographing portion may beautomatically set. In this case, radiation quality adjustment issubstantially determined by the tube voltage of the X-ray tube 100. Theobject region is extracted using the object position informationacquiring means and object region extraction means of theninth/embodiment, and is compared with head, breast, abdomen, hand, andleg photographing portion look-up tables, which are prepared in advanceby pattern matching, thus determining the photographing portion.Recommended tube voltage look-up tables prepared in units of portionsare looked up for the determined portion, and the tube voltage foractual photographing is automatically set or is displayed as arecommended tube voltage.

What is claimed is:
 1. A radiographic apparatus comprising: aradiographing unit for radiographing an object irradiated with radiationand obtaining radiographic image data; a detecting unit for detecting asurface of the object and obtaining surface data; and a body-partspecifying unit for specifying a part of the object to be radiographedby said radiographing unit based on the surface data.
 2. An apparatusaccording to claim 1, further comprising a unit for determining acondition for radiographing the object based on body-part informationobtained by said body-part specifying unit.
 3. An apparatus according toclaim 1, further comprising a unit for determining a condition for imageprocessing of the radiographic image data based on body-part informationobtained by said body-part specifying unit.
 4. An apparatus according toclaim 1, wherein said detecting unit detects an image of the surface ofthe object as the surface of the object.
 5. An apparatus according toclaim 1, wherein said detecting unit detects position of the surface ofthe object as the surface of the object.
 6. A radiographic apparatuscomprising: a radiographing unit for radiographing an object irradiatedwith radiation and obtaining radiographic image data; a detecting unitfor detecting a surface of the object and obtaining surface data; and aposture specifying unit for specifying posture of the object based onthe surface data.
 7. An apparatus according to claim 6, furthercomprising a unit for determining a condition for radiographing theobject based on posture information obtained by said posture specifyingunit.
 8. An apparatus according to claim 6, further comprising a unitfor determining a condition for image processing of the radiographicimage data based on posture information obtained by said posturespecifying unit.
 9. An apparatus according to claim 6, wherein saiddetecting unit detects an image of the surface of the object as thesurface of the object.
 10. An apparatus according to claim 6, whereinsaid detecting unit detects position of the surface of the object as thesurface of the object.
 11. A radiographic apparatus comprising: an X-rayradiation unit for irradiating with radiation; a radiographing unit forradiographing an object irradiated with the radiation and obtainingradiographic image data; a detecting unit for detecting a surface of theobject and obtaining surface data; a photo timer for controlling saidX-ray radiation unit on the basis of a radiation amount which isreceived by a radiation receiving part of said photo timer; a body-partspecifying unit for specifying a part and/or a posture of the object tobe radiographed by said radiographing unit based on the surface data;and a gain-specifying unit for determining gain of said phototimer inaccordance with an identified posture of an object or an identified partof the object.
 12. A radiographic apparatus comprising: an X-rayradiation unit for irradiating with radiation; a radiographing unit forradiographing an object irradiated with the radiation and obtainingradiographic image data; a detecting unit for detecting a surface of theobject and obtaining surface data; a body-part specifying unit forspecifying a part and/or a posture of the object to be radiographed bysaid radiographing unit based on the surface data; and aquality-specifying unit for determining quality of the radiation inaccordance with an identified posture of an object or an identified partof the object.
 13. A radiographic apparatus comprising: a radiographingunit for radiographing an object irradiated with radiation and obtainingradiographic image data; a detecting unit for detecting a surface of theobject and obtaining surface data; and an area specifying unit fordetermining a reading area of said radiographing unit on the basis ofthe surface data.
 14. An apparatus according to claim 13, wherein thearea specifying unit determines the reading area of said radiographingunit on the basis of an object region which is calculated by imageprocessing the surface data.
 15. A radiographic apparatus comprising: aradiographing unit for radiographing an object irradiated with radiationand obtaining radiographic image data; a printer for printing theradiographic image data on a film; a detecting unit for detecting asurface of the object and obtaining surface data; and a film sizespecifying unit for determining a film size of said printer on the basisof the surface data.
 16. An apparatus according to claim 15, wherein thefilm size specifying unit determines the file size of said printer onthe basis of the object region calculated by image processing thesurface data.